As part of the investigation, agents are trying to determine whether a woman's DNA found on a piece of a pressure cooker used as an explosive device in the attacks was from Katherine Russell, the wife of Tamerlan Tsarnaev, the New York Times reported.

FBI agents visited the North Kingstown, R.I. home of Tsarnaev's in-laws Monday and carried away several bags.

A DNA sample from Russell was taken by the agents, several media organizations reported.

The authorities are looking at a range of possibilities, two senior law enforcement officials told the New York Times, including that she could have - wittingly or unwittingly - destroyed evidence, helped the bombers evade capture or even played a role in planning the attacks.

FBI spokesman Jason Pack confirms agents went to the home of Russell's parents Monday. Russell has been staying there.

Russell did not speak to reporters as she left her attorneys' office in Providence later in the day. Attorney Amato DeLuca says she's doing everything she can to assist with the investigation.

"We want to state what we stated before: Katie continues to assist in the investigation in any way that she can," he said in an e-mail to the New York Times.

Tamerlan Tsarnaev may have been in touch with suspected militants before and during his visit last year to southern Russia, ABC News reported.

American officials are investigating whether Tsarnaev had been in contact over the internet with a man named William Plotnikov, a Russian-Canadian and a fellow boxer, who had converted to Islam and joined the militant insurgency in the North Caucasus.

Authorities also want to know what Tsarnaev was doing with a known militant recruiter in the region named Mansur Mukhamed Nidal with whom Tsarnaev was repeatedly seen leaving a controversial mosque in Makhachkala, the capital of Dagestan.

Tamerlan Tsarnaev was killed in a gun battle with police. Dzhokhar Tsarnaev has been charged with using a weapon of mass destruction.

Minute-by-minute: How bombers attacked, evidence hidden

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New information continues to emerge about the two suspects in the Boston Marathon Bombing. Federal documents breakdown how the Boston Bombing suspects reportedly carried out the attack, and show how close friends attempted to hide evidence from investigators.